Process of producing cellular material



K. H. FULTON.

PROCESS 0F PRODUCING CELLULAR MATERIAL.4

APPLlcATxoN FILED mAYe,192o.

Patented July, L99 192k PATENT-orner.

KARL H. FUTON, 0F PIT-'.ISB'UMH, PENNSYLVANIA rgaeaoaa To all whom t mayo o/:wem: be it known that ll, KARL H. FULTON, c1t1- `zen of the UnitedStates of America, re-

siding at 220 Shad avenue, Pittsbur h, in

,the county of Alleg eny and State of ennsylvania, have invented certainnew a d useful Improvements ilu-Processes or roduc'- ing CellularMaterial, ofvvhichV the followingjis a specification.

he invention relates to a process of producing cellular material.

It is an objecto the invention to provideI a process for producingcellular rubber, having a multitude of separate as bearin cellsarrangedthroughout the bo y thereo lt is a further object of the invention toprovide a process wherein relatively soft cellular rubber articles, orrelatively hard cellular rubber may be produced for use in variousields.

The invention is based on the discovery that vcertain granularsubstances when incorporated ina body of rubber and subjected to theaction ot a gas under pressure, possess the characteristics of absorbingor occluding in the voids or interstices of the granules appreciablequantities of the gas without effecting a change in the size orformation of the granules. lf the material,

While still subjected to the gas under pressure is given a vulcanizingtreatment, the rubber will be vulcanized around the infinite number ofminute gas bearing granules v:forming coatings or envelops for thegranules. The gas occluded in the granules oes not escape during thevulcanizing treatment whichis carried on in the presence of the gasunder pressure, and ater'the vulcanization the material is cooled whilestill under gas pressure to prevent the liberation of the occluded gas.To form the cellular material the vulcanized l product Ais then againheated when the gas pressure has been released, the occluded gas of eachgranule then escaping or being released expanding the elastic materialforming a coating therefor, thereby' producing in the body an innitenumber of separate gas cells. formation of each cell; is produced by thereleasing of the occluded gas or the granular part1clevvhich assumes avolume several times of that of the original particle v thereby expandinthe cell an appreciable extent which may e controlled by the pres.-

Speciication of Letters Eatent.

' Application med May 6, 1920. Serial No. 3?9,308.

The

PROCESS 0F PRDUCI CELLULAR MATERIAL.

Paten ed July 19 sure of the gas when the particles are irst sub ectedto the action thereof.

he final volume of the cellular rubber depends upon the number of cellsformed therein, and also upon the amount of gas 1n each cell. lt will beapparent that the to the number of particles of the granularmaterialemployed in the originalv mixture.

ln carrying out the present process l preferably intimately mix raw Pararubber, with a suilicient quantity of sulfur to bring aboutvulcanization, and the linely divided granular material vvhich ispreferably a material such as activated charcoal. IThis material iscommercially manufactured by the dry distillation of dense vegetablematerial,such as cocoanut shells, peach kernels, and the like, and llhave discovered that it possessesv the characteristic of absorbing oroccluding relatively large quantities of as when subjected thereto underpressure. 'lghe material is preferably comminuted or pulverized to avery fine mesh, as for'` example a hundred mesh, and when thoroughlymixed with the raw rubber is shaped into a' desired form depending uponthe use of found that an inert gas such as nitrogen is hi hly eilicientin performing the process.

Vhen the mixture is thus shaped the material is introduced to areceptacle which is sealed or formed in any. convenient manner toprevent the escape of gas-therefrom,

and the inert gas such as nitrogen is then introduced to the receptacle.rThe gas is readily occluded by the charcoal and finds lodgment in eachof the minute voids or interstices thereinA throughout the infinitenumber of granules, but the occluded gas does not edect a change inshape or size of the mass in any Way. The gas thus comes vin directcontact with the rubber ymass, and

enters the activated charcoal as described,

above. After being subjected to the action ofthe gas for the desiredperiod, the rubber is then vulcanized by subjecting -the same to thenecessary heat treatment, attention being called to the fact that duringthe vulcanization of the rubber the pressur@ of the inert gas 'ismaintained, and

also after vulcanization the vulcanized mass is cooled in the presenceof, the nitrogen gas still maintained in the container at its originalpressure to prevent the charcoal from giving'up this occluded gas whenthe pressure is later released. It will be observed that by maintainingthe gas pressure Vduring the' vulcanization of the rubber, and

`also after Vulcanization, and while the mass leased, and to thevulcanized rubberenough heat is then applied to cause the particles ofcharcoal to give up all the occluded gas. This occurs in View of thefact that during the second heating there is no gas pressure to prohibitthe occluded gas from'escaping from the charcoal, each particle of whichbecomes the nucleus of a small gas cell. The heating 0f the vulcanizedrubber when the pressure has been released, causes the oc eluded gas tobe driven or released from the particles of charcoal, the volume or sizeof each particle of charcoal being exceedingly small as com ared withthe volume of oceluded gas. The discharged gas swells this confiningenvelop or cell which assumes a size several times that of the originalcell.

It will be understood that by the provision ofthe infinite .number ofparticles of charcoal, a corresponding number of cells is formed in therubber, and that each'cell is individually sealed. The resulting mass ofcellular rubber is of the same configuration as the original materialprior to its, heating and vulcanization, but greatly increased in sizein all dimensions because of the formation of the multitude of gascells.

It has. been found that the size the original rubber mass is to assumewhen in a cellular form depends of course-in part upon the number ofcells formed by the granular particles of charcoal, and the amount ofgas confined in each cell. The number of cells, is, as before stated,equal to the number of charcoal particles used in the mixture, While thesize of each cell depends upon the pressure of the gas when the materialis rst subjected to its action. The greater the pressure, manifestlymore gas is occluded in the particles thereby forming a larger cell whenthe occluded gas is released by the final heat treatment.

While the cellular material may be formed from thecomposition ofysubstances above described when used in various quantities, I havefound that al highly eiiicient cellular rubber can be produced by theemployment of activated charcoal to the extent of approximately three tolive per cent. of t e total of the other in redients, that is the rawrubber and its vu canizing agent which may be sulfur, etc. The guantityof sulfur may range from ve to teen per cent. for the production of goodresults, and instead of sulfur antimony sulfid, sulfur or mixtures ofsulfur and antimony suld and many other vulcanizing agents oracceierators maybe employed.

In carrying out the present process no particular form of apparatus need'essentially be employed, but for the sake of clearness I have disclosedin they accompanying drawing a type of apparatus'which may besuccessfully employed to support the process; This apparatus is simplyshown for the purp'ose of illustration, and not for limitation, and Iwish it to be distinctly understood that the process is one thatissusceptible of being carried into use by many forms of apparatus widelydifferent from that disclosed in the present drawing forming a part ofthis application. v

In the drawing Figure 1 represents a section view through the apparatus.

Referring now more particularly to the drawing wherein like referencecharacters indicate corresponding parts' the numeral 1 designates a gastight cylinder or container which may be of any convenient shape andsize. This container is provided with a removable closure 2.

The top 2 is united to the body of the container by means of thefastening devices 4 to' form a sealed connection between the con tainerand its closure, a suitable packing or the like being employed ifdesirable. The y container 1I is also formed by the provision of aspaced wall 5 with a acket 6 for receiving the heating and coolingagent.

Leading to the container 1 is a gas feeding pipe '7 controlled by thevalve 8, the pipe leading from a suitable gas supply and adapted toconvey gas to and from the container under a regulated and Variablepressure. The material to be treated consists of the mixed rubber,vulcanizing agent and the multitude of granular particles of activatedcharcoal which has been kneaded or shaped to the desired configuration.

The shaped material'is then placed in the vcontainer 1 and subjected tothe action of 'pressure of the gas entering the container.

The material is then subjected to a vulcanizing temperature by theintroduction of a heating medium, which may be steam, water and the likeconveyed to the jacket 6 by the neonata feed pipe 9 and drained outthrough the still being subjected to the action of the inert gasunder'pressure. After the rubber has.l been vulcanized the gas is stillmaintained under ressure in the Vcontainer l and a cooling me iumintroduced to the jacket throu h the pipe 10, and out'through pipe hiscooling medium serves to prevent the escape of the gas from thepartlcles ot charcoal when thepressure is later released, forming'4tenaceous envelope 4surrounding each particle of charcoal which islater to constitute a gas cell.

'"When the cooling has progressed to the desired degree, Vthe coolingmedium. is discharged from the achet 6 andthe gas pressure in thecontainer 1 released until the material is subjected to an atmosphericpressure. The mass is then again heated b the introduction of a heatingagent throug the feed pipe 9, to a temperature approximately 200 degreesFahrenheit for a period of several hours, which causes the -particles ofcharcoal, each individually encircled or in-V closed by an envelop or'lilm of the rubber to release its occludedl gas, and as the size of eachparticle of charcoal is so small as'compared with the volume of occludedgas absorbed thereby, the envelop surrounding the occluded particleiscaused to swell by the suspending gas several times that of itsoriginal size. It will be observed that this last heating step isperformed While the material is no longer under the action of thenitrogen gas under pressure, and hereit might be mentioned that the sizeof each gas cell is primarilyv dependent upon the pressure et the gas towhich the material is originally subjected.

ln following the present process products adapted for manydiilerent'uses maybe made, this generally, depending upon the kind ofrubber usedy lfl it is desirable to produce a' hard vulcanized cellular'rubber which does not possess'much resiliency, all Para rubber is usedin the mixture with an excess of sulfur lto carry the vulcanization to acompletion. The gas 'is or course occluded in the particles during thisvulcanization, and subsequently released, forming a hard cellular rubbermass Vof high tensile strength which may be fashioned inthe form ofboards and the like, applicable for use as a hard insulating materialfor linin s for refrigerators, refrigerator cars and te like. lnproducing the hard .vulcanized cellular rubber of this character, thevulcanization is not carried to completion when the article is rstsubjected to heat, but merelyv to a stage to produce a sott cellularrubber.y After this preliminary heating orl Vulcania-tion the material.is again subjected the body or the tiller.

to the action of a vulcanizing temperature until complete vulcanizationhas taken place. 'lo obtain boards or the like having rela'- tivelysmooth surfaces, the iinal"'vulcanizing step is preferably accomplishedin a press.

providing smooth surfaces.

To provide a sott cellular article, or cellu.

lar rubber which is veryspongy, a mixture of Paraand balata rubbers isused, mixed with the proper quantities of sulfur or like vulcanizingagent and the granules of charcoal. This material is then subjectedtothe treatments described in de'ning the main process and the articlesproduced are particularly useful as 'heat insulating, and water procngmaterials, upholstery, mattresses, and the like.

The present' process also contemplates the l production of tirefiillers' or like articles which naturally must possess a great amountof'resiliency. ln manufacturing tire fillers having aA thickness ofseveral inches or more it has been found necessary that during theshaping of the original mixture of Para and balata rubbers and the otheringredients to insert numerous continuous ibrous filaments in the4original rubber mixture. These lilaments Arun from end to end of theymixture and serve to provide passageways for the inert gas to permeatethe multitude of the charcoal particles distributed throughout the bodyof the mixture. This is of course requiredl in order that the gas maycome v1n v contact with and be absorbed or occluded in;

the activated charcoal particles which lie in he mass is then vulcanized`While under the influence of the gas pressure and cooled before the gaspressure is released. Betere the final heating to release the gasoccluded in -the charcoal. particles the iller is preferably placedWithin a tire shoe mounted upon a rim and the entire assembly subjectedto the second heating action.` This causes the occl-uded gas to `bedriven from the charcoal particles'and a consequent expansion of thefiller so as to completely ll the interior of the tire shoe, because thepressure of the nitrogen gas has been released. 'Y 4 ln theforegoing'speciication I have only described a few of the uses ot thevmaterial produced by this process, but it will of course be understoodthat the process is susceptible of producing materials which are usefuland applicable in unlimitedl the presence ot gas under ressure to beabsorbed by said gas occlude particles, in vulcanizing the materialWhile being subjected to the gas pressure, 1n allowmg the material tothen cool, and in finally heating the maf terial to cause the occludedgas to bedischarged from the particles forming in the material a,multitude of gas cells.

2. The process of producing cellular Irubber, comprising the intermixingofV raw rubber with divided granular materia-l susceptible of occludinggas, in subjecting the mixture to the action of a gas under pressurewhereby the granular particles occlude appreciable quantities of thegas, in vulcanizing the material while still being subjected to theaction of the gas under pressure, and in finally permitting the occludedgas of the Granular 4llgarticles to be discharged to form in the rub erbody a multitude of gas beari ing cells by subjecting'the same to theheat treatment in the absence of the gas pressure.

3. The process of manufacturing cellular rubber, comprising the mixingof raw rubbei' and finely divided activated particles, in subjecting'thematerial to the action of an inert gas under pressure to be absorbed bythe activated particles, in vulcanizing the material to form envelopssurrounding the ranular vparticles having occluded gas, and

1n then vheating the material after the gas l pressure has been releasedto cause the occluded gas to be discharged from theparticles forexpandin the formed envelops, and producing in t e mass a multitude ofseparated gas cells.

4:. The process of manufacturing cellular rubber, consisting inintroducing to raw rubber a nely divided granular material'susceptibleof absorbing gas, in subjecting the mixture to the action of a gas underpressure, whereby the granular 4material absorbs appreciable quantitiesthereof, in vulcanizin` the material in the presence o-f the gas un erpressure, in cooling the material, and in then heating the materialafter a releasing of the gas pressure to cause the granular particles togive up their absorbed gas and produce in the rubber a multitude ofseparated gas cells.

5. The process of producing cellular rubber, comprising the intermixingof raw rub- Vber with comminuted articles of activated.

material, in absorbing 1n the particles a gas, in vulcanizing thematerial to form coatings surrounding the comminuted gas bearingparticles, and in then heating the material to cause the as contained inthe particles to be in the rubdischarge therefrom producing u earingces.

ber a multitude of separated gas 6. The process of manufacturingcellular rubber, comprising the intermixing of finely divided ranularmaterial with raw rubber, in su jecting the intermixed material to theaction of an inert gas under a variable regulatable pressure to causethe granular particles to absorb a quantity of the gas, in

jecting the mixture to the action of a Vgas under pressure tocause thegranular material to absorb'gas, invulcanizing the mixed substanceswhile under pressure, lincooling the material after vuloanization, inreleasing the as pressure after cooling, and in then heating thematerial to cause the occluded gas to be discharged from the granularparf ticles forming a multitude of rubber cells.

8. The process of producing cellular rubber whichV consists in mixingwith rubber forming material gas occluding' particles, in vulcanizingthe mixture and in allowingthe same to then cool, and in finally heatingthe material when in alcool state to cause the oceluded gas-of 'the`particles in the material to be released forming therein a multitude ofnoncommunicating gas cells.

9. The process of producing cellular rubber which consists in mixing therubber and gas occluding particles, in subjecting the mixture to thepresence of gas, in vulcanizingthe mixture, in allowing the vulcanizedproduct to cool, and in finally heating the material tocause theparticles to giveup their occluded gas forming in the material amultitude of noncommunicating cells.

In testimony whereof I aiiix my signature.

KARL H. FULTQN.

